Esters of primary acetylenic alcohols as tetraalkyl lead appreciators



United States Patent 3,198,612 ESTERS 0F FREMARY ACETYLENIC ALCOHGLS AS TETRAALKYL LEAD APPREiZIATQRS Qhien-Wei Liao, Beachwood, Ohio, assignor to The tandgrd @il Company, Cleveland, Ohio, a corporation of mo No Drawing. Filed Sept. 29, 1%2, Ser. No. 225,157 2 Claims. (Cl. 4469) This invention relates to a highly aromatic and olefinic leaded motor fuel composition with a high octane rating. More particularly, it concerns the addition of a novel lead appreciator or extender in a small amount to the leaded motor fuel to increase its octane rating.

The lead appreciator used in the invention is the ester of a primary acetylenic alcohol with the formula:

where R is selected from the group consisting of hydrogen and an alkyl group containing 1 to 3 carbon atoms, and R is an alkyl group containing 1 to 3 carbon atoms. These compounds, together with a tetraallryl lead in a high octane motor fuel with a large aromatic and olefinic content, increase the antiknoch qualities appreciably when used in amounts ranging from 0.1 to 3% by voltime, preferably at least 0.5%, and desirably about 1%.

Today, the increased octane rating of motor fuels is a concomitant of the increased compression ratois of automobiles. To meet this demand for higher octane fuels, refineries have installed such process operations as cracking units to form olefins or reforming units to form aromatics. Olefins and aromatics have higher octane ratings than many saturated hydrocarbons in the same boiling range. They do not, however, respond as favorably with tetraalkyl lead. When the aromatics and olefins in motor fuels are increased to attain the octane values required by the high compression engines, the effect of the tetraalkyl lead is decreased.

Fuel antiknock is not a single factor, but is a combination of factors, such as fuel composition, engine design, operating and environmental conditions. Tetraalkyl lead is very unstable and decomposes rapidly in a high compression ratio engine, even before it is used by the advancing flame front. It is postulated that it is not the tetraalkyl lead itself which is responsible for antiknock but it is a product of its decomposition, probably lead oidde. At the same time that the tetraalkyl lead antiknock species is released, a reaction takes place that consurnes the antiknock species. It is the agglomeration of the lead oxide which causes a reduction of its surface and dispersion. The tetraalkyl lead extenders are believed to interfere with the undesirable agglomeration of lead oxide. Thus, the extender prolongs the life of the lead oxide of the efiective antiknock species until a critical time in the engine cycle. Tetraalkyl lead decomposes earlier in the engine cycle with the increased compression ratio; Whereas, the reaction causing the knocking occurs, at a fixed time cycle. Above a certain compression ratio, tetraalkyl lead decomposition does not occur at the critical stage in the reaction that results. A gap occurs be tween the time when the tetraalkyl lead decomposes and the time when the antiknock species are needed. At this point, the antiknock species effectiveness is hindered by lead agglomeration.

A proposed mechanism for the function of tetraalkyl E,l9.8,6l2 Patented Aug. 3, 19%5 ice lead appreciators, when the ester is an acetate, is as follows:

agglomeration TEL .PbO (PbO) Antiknock Ineffective compound compound Appreclator acetic acid PM) 2acetic acid Pb(OOCGH )1 11 0 I PMC0001192 PbO 00, omc iom acetone The formation of lead acetate is the key step to this action. Lead acetate is pyrolyzed to lead oxide at a later and more propitious time to coincide with the formation of the aromatic knock-causing compound formed later in the combustion cycle.

The principal object of this invention is to increase the octane number of leaded motor fuels containing substantial amounts of aromatics and olefins by adding a lead extender that is an ester of a primary actylenic alcohol.

The order of decreasing resistance to pyrolysis of esters is primary, secondary, and tertiary. Since tertiary esters form olefins on pyrolysis and are more easily pyrolyzed than secondary or primary esters, it has been thought that only esters of tertiary alcohols display effectiveness as lead appreciators. It is unexpected, then, to find that a primary ester should display effective lead appreciation.

The esters of primary acetylenic alcohols are eifective lead appreciators, because they form highly conjugated systems that are easily pyrolyzed forming the parent carboxylic acid, the actual effective lead appreciator compound. It is believed that a bi-molecular decomposition mechanism shown by the following equation in which the hydrogens and carboxylic radicals from the different molecules are detached to form carboxylic acid molecules is involved.

For example, when the carboxylic acid is acetic acid, the decomposition of 2-propyne-l-acetate is as follows:

Acetic acid Highly conjugated The propionate and the butyrate embraced within this invention react in a fashion analogous to the acetate. However, they react slower and on a volume basis more are required to achieve equal mole amounts. For that reason, the acetate is preferred. The alkyne radical is less critical; butyne, pentyne, and hexyne carboxylates dissociate with great ease but in their case similarly larger weight and volume amounts are required which render them less economic than the propyne esters.

Any fuel may be employed which boils in the gasoline range, contains at least 1 and up to 6 ml. of tetraalkyl lead per gallon, has a Research octane number of at least 90, preferably 99, and an aromatic and olefine content totaling at least preferably 40% by volume.

The tetraalkyl lead may be tetramethyl lead or tetraethyl lead or chemical or physical mixtures thereof, such as dimethyl, diethyl lead; monethyl, trimethyl lead or mixtures thereof; tetramethyl and tetraethyl lead; or mixtures of these two or mixtures of either or both with 3 any of the mixed alkyl leads. The usual halide scavengers may be employed, but their presence is not essential to achieve the beneficial effects of the invention.

In addition to the tetraalkyl lead and the lead appreciator,'the motor fuel may contain any of the usual additives, such. as antioxidants, top cylinder lubricants, surface ignition modifiers, such as phosphorus and boron compounds, carburetor detergents, anti-icers, etc.

The 2-propyne-1-acetate was prepared as follows:

A 56 gram or 1 mole amount of 2-propyne-1-ol and an excess amount, 204.2 grams or 2 moles, of acetic anhydride were heated at 124 C. for 4 hours. The catalyst was four grams of sodium acetate. After the reaction was complete, an aliquot of the reaction mixture (equivalent to 0.434 mole of 2-propyne-1-ol) was neutralized with an aqueous solution of sodium bicarbonate to remove the acetic acid formed as a lay-product and the excess reactant acetic anhydride. It was extracted with ethyl ether after which it was dried with sodium and magnesium sulfates.

After distillation, a yield of 73.3 grams (75.6% of theoretical) of a clear, colorless liquid was obtained.

It has a boiling point of 108 C. at 760 mm. of mercury and a refractive index at 25 C. at 1.4155. Infrared absorption confirmed the structure.

Standard ASTM Research and Motor methods for rating laboratory octanes were the basis for all the data recorded. All the fuels were rated three times.

T est fuel A Volume, percent 230 F.+cat. ref 40 Tot. cat. dist. 40 SR naphtha 20 Fluorescent indicator analysis (Fl/1) Volume, percent saturates 41 Olefins do 21 Aromatics do 35 TEL ml./gal. 3

Engler distillation: F IBP 116 50% 258 95% 404 4 TABLE I.EFFECT OF Z-PROPYNE-l ACETATE ADDITIONS ON MOTOR FUEL OCTANE RATINGS Experimental results. The effectiveness of the esters of primary acetylenic alcohols as tetraalkyl lead extenders is illustrated by the data collected for Z-propyne-l-acetate in Table I. The data shows that improved octane ratings are obtained in both the motor and research methods.

The appreciable increase in the octane rating motor method is especially significant since the method for determining octane rating is a more test than the research method.

I claim:

1. A high octane gasoline containing 1 to 6 mls. of tetraalkyl lead per gallon, an aromatic and olefin content totaling at least 30% by volume, and to which has been added a lead appreciator with the formula in the motor severe wherein R is selected from the group consisting of hydrogen and alkyl having 1 to 3 carbon atoms and R is an alkyl group having from 1 to 3 carbon atoms in an amount within the range of 0.1 to 3% by volume.

2. The composition of claim I in which the ester of the primary acetylenic alcohol is 2-propyne-l-aoetate.

References Cited by the Examiner UNITED STATES PATENTS 2,210,942 8/ Lipkin 44-70 2,228,662 1/41 Helm 4470 2,899,391 8/59 Mayhew 4470 FOREIGN PATENTS 320,132 9/60 Australia. 571,921 10/53 Belgium. 837,965 11/38 France.

DANIEL E. WYMAN, Primary Examiner. 

1. A HIGH OCTANE GASOLINE CONTAINING 1 TO 6 MLS. OF TETRAALKYL LEAD PER GALLON, AN AROMATIC AND OLEFIN CONTENT TOTALING AT LEAST 30% BY VOLUME, AND TO WHICH HAS BEEN ADDED A LEAD APPRECIATOR WITH THE FORMULA 